The present invention relates to a hydrodynamic retarder including a rotor on a shaft, a stator, and a toroidal work chamber, in which the rotor and the stator are hydrodynamically coupled by respective blade wheels on the rotor and the stator located in the work chamber. The invention particularly relates to means for filling and emptying the work chamber.
Particularly when the hydrodynamic retarders are used in automotive vehicles or in systems with strongly varying operation, such retarders are connected and disconnected by filling and emptying the work chamber. For this purpose, working liquid is fed through suitable channels and past a prior control device to the work chamber or work space of the retarder. Removal of the working liquid from the work chamber is preferably radially outward via a slot located between the rotor and stator blade wheels.
Federal Republic of Germany Patent No. 35 11 795 discloses a hydrodynamic retarder in which the working liquid is introduced through channels in the blades of the stator directly into the so-called core ring of the retarder. There the lowest pressure prevails within the flow. As a rule, there is a hollow space that is not filled by the working liquid in the core ring even during operation, so that the retarder can be filled from a filling pump with only a slight expenditure of energy. The channels necessary for filling the work space are either cast directly into the blading or are subsequently welded therein. In either case, a channel path through the blades is connected, producing a sensitive local thickening of the blades in question. This leads to a considerable disturbance in the flow through the blading.
A hydrodynamic retarder is known from U.S. Pat. No. 2,126,751 in which feeding of the work liquid is effected via plates which are provided with slots, and the plates are arranged turnably on both sides of the stator blade wheel. The slots are of different widths. Depending upon the position of rotation of the plates, the slots come into alignment with channels which are cast into the blading of the stator blade wheel. However, these are control slots for dosaging the amount of working liquid flowing to the retarder and are not working liquid inlet or outlet slots.
Federal Republic of Germany Application DE-OS 16 75 246 discloses a retarder having blades which are also free of channels for the filling or emptying of the work space. The working liquid passes through an annular slot formed between the blade wheels and into the work space, and the liquid emerges from the work space via a similar slot arranged radially on the outside. The passage of the flow from one blade wheel to the other thus results in a considerable disturbance in the flow.
One skilled in the art knows that even in the case of a retarder whose flow is completely converted into heat by eddying, the power that is absorbed and the braking torque that is developed can be increased if the blading results in a flow which is as free of surges and is as undisturbed as possible. In the case of cast channels, this means careful rounding out of the differences in the thickness of the blades, and that in turn means an increased expense for material and a greater weight. In the case of welded channels, a flow favorable development within the thickness of the blade can be obtained only at a very particularly high manufacturing expense.